Conventionally, an adaptive modulation/demodulation scheme that can change a digital modulation scheme by transmitting channel state information to a transmitter based on a signal received from a receiver of a high-speed Wireless Personal Area Network (WPAN) communication system is widely used. This method can ensure a maximum transmission rate without data error. In terms of hardware embodiment, the method can adaptively change the digital modulation scheme to optimize a calculation complexity of the receiver, and thereby can reduce power consumption to an extent. However, the method is a long way from an adaptive modulation and demodulation in associated with a active power resource management.
The adaptive modulation is known as one of various technologies that supports a high-speed wireless communication. A basic concept of the adaptive modulation is to change a modulation scheme according to a channel state, and basically to use a time-varying feature of a fading wireless channel instead of to avoid fading in the wireless channel.
Meanwhile, the bit resolution is a scale that indicates how close a converted digital signal is to an original signal, namely, an analog signal, when the A/D converter converts the analog signal into the digital signal. That is, as the bit resolution is higher, the signal converted into the digital signal gets closer to the original analog signal, and as the bit resolution is lower, a quantization error value between the signal converted into the digital signal and the original analog signal gets greater. As the quantization error value is greater, a digital signal processing result may provide inaccurate results, and thus performance of the receiver decrease.
In other words, generally, as the bit resolution is higher, a rate that the A/D converter can handle may decrease. Also, since as the bit resolution increase, power consumption increase relative to the increase of resolution and a digital signal output value becomes fine, there may be a problem that a digital circuit becomes complex.
However, as the bit resolution is higher, the digital signal output value becomes more accurate, thereby increasing accuracy of a circuit output value and improving performance.
A high-speed WPAN system is one of various technologies that can change digital media to a wireless form. For example, due to requirements of a high-speed transmission, such as communication from a notebook computer to a beam projector, communication from a set top box to a high-quality television, and the like, communication that is only possible with a wired cable is currently considered to be used with wireless communication. Specifically, Institute of Electrical and Electronics Engineers (IEEE) 802.15 WPAN, which is the International Standardization Organization for utilization as described above, has an affiliated organization, TG3c. TG3c has determined a carrier frequency for the wireless communication as 60 GHz. This is the reason the WPAN system for the utilization is referred to as a millimeter-wave WPAN system, and there are efforts for standardization of the system. However, there are a lot of difficult problems in the WPAN system based on the millimeter-wave. For example, in the case of a Radio Frequency (RF) technology of a millimeter-wave frequency band, it is considered one of the most difficult problems in millimeter-wave based WPAN system technologies, since the RF technology is required to be embodied based on an RF technology using complementary metal-oxide-semiconductor (CMOS) to embody an inexpensive RF device or an RF technology which is comparable with the CMOS in view of price. Due to international interest with respect to an RF-CMOS technology in a millimeter-wave frequency band, the technology of today can embody an RF technology based on CMOS technology in a 60 GHz frequency band. Also, an RF-CMOS is nearly commercialized. Another difficult problem in the WPAN system of a millimeter-wave frequency band is embodiment of an A/D converter that supports a transmission rate of several gigabits. That is, a minimum required transmission rate of a High-Definition Multimedia Interface (HDMI) that IEEE 802.15.3c considers is 2.5 Gbps, the HDMI being a utilization of the WPAN based on the millimeter-wave. In this instance, to process the transmission rate of 2.5 Gbps in a digital communication, the A/D converter is required to perform sampling data at a rate of at least 5 Gbps in view of Niquist. Considering an A/D converter technology of today, it may a heavy burden. For example, an A/D converter that supports five to six bits per sample is generally used, to ensure reasonable performance requirement. Supporting HDMI of 2.5 Gbps is inappropriate for the WPAN system, since the A/D converter technology of today consumes a great amount of power to support five to six bits at a rate of 5 Gbps.